What materials do you most commonly use on your robots?

[Mark Sheridan]

Originally Posted by mman1506

Any ideas for what to do with these 3/4 to 3 inch thick sheets of scrap T6 hardened 7075 aluminium we were donated?
https://fbcdn-sphotos-d-a.akamaihd.n...86326484_n.jpg

We've been thinking of making a 7075 belly pan

That is a nice chunk of scrap. Perfect for FRC sized parts.

[Oblarg]

Originally Posted by mman1506

Any ideas for what to do with these 3/4 to 3 inch thick sheets of scrap T6 hardened 7075 aluminium we were donated?
https://fbcdn-sphotos-d-a.akamaihd.n...86326484_n.jpg

We've been thinking of making a 7075 belly pan

Holy crap, that's a lot of metal.

Got a CNC mill?

[mman1506]

Originally Posted by Oblarg

Holy crap, that's a lot of metal.

Got a CNC mill?

We do

[Oblarg]

Originally Posted by BurkeHalderman

Can you describe these mechanical failures that were caused by using 80/20?

I'd assume it'd be due to parts shifting in the T-slot profile. However if you simply drill through the 80/20 after positioning it using the T-slot then the problem is resolved.

You're correct in your assumption. The problem, and it is a pervasive problem, is that in the rush of build season, taking apart everything and through-drilling all of the 80/20 parts that need to be through-drilled simply doesn't end up getting done - human psychology being what it is, I've simply noticed that it's not at all hard to leave something improperly constructed and sloppy on an 80/20 frame where, at a glance, it seems functional. Building final versions out of other materials ends up being lighter, not much more work, and ensures that everything ends up rigid and fixed in place.

If students (and mentors) were perfect, this would not be an issue, but as I mentioned earlier I feel it's as much a pedagogical concern as it is a functional one. I (and the rest of my team, from what I recall) got into a bunch of nasty habits in my early FRC years with 80/20 construction that took a while to break. I feel it is far safer to avoid them entirely.

I do think we probably ought to wrap this exchange up, lest we fully derail the thread; we could start another, if you'd like to continue discussing it.

Originally Posted by mman1506

We do

Then the possibilities are endless!

[Brandon Zalinsky]

Just to keep with my team's namesake...

PVC tubing is very effective when you need a lightweight material for arms and other manipulators. It also makes an efficient roller or spacer.

[BBray_T1296]

Originally Posted by BurkeHalderman

The 1" square profile, at .59lbs/ft is barely heavier than a 1" square, 1/8" wall aluminum tube at .524lbs/ft. So no it is not heavy. If you use 80/20 with an absurd amount of gussets then yes your robot is going to be heavy, if used properly it is not heavy.

I have never seen a team use .125 thick 1" tubing. Everyone I've seen (including our team) uses .0625 (1/16") wall thickness, which, without running numbers (or Google-ing), should end up roughly 1/2 that weight per foot.

[seg9585]

I like using 80/20 for chain and belt tensioning, easy way to move the belt around and loosen then tighten it. Did this to tension our shooter arm pivot chain last year.
PVC tubing is always great to make spacers and as a circular form of shielding.

I havent gotten into carbon fiber construction in any robot's I've mentored teams for yet, but we have the resources to do so this year so it may be fun to try. I have personally done CF layups (both vacuum seal + autoclave and wet) so have some experience with the process. Just gotta get the students on-board first.

[Celia]

240 tends to use aluminum tubing, polycarbonate, and wood for general constructions. As previously stated, we like PVC for spacers. It seems like these are the go-to materials for many teams. However, we're testing out some corrugated plastic soon, so maybe that will be added to the list

[Jared]

Originally Posted by BBray_T1296

I have never seen a team use .125 thick 1" tubing.

We used it this year on some frame parts and our climber mounts, but we think we could have gotten away with the thinner stuff. When we fell of the tower we had a weld snap before the box tubing bent. We also have a TON of it in storage, so we'll probably end up using it again.

[Pendulum^-1]

Mostly aluminum. Our chassis is typically c-channel, and the superstructure is a lot of 8020. If anyone is using 8020, I highly recommend that you use their " end fasteners." Very lightweight and strong way to make right angle joints in 8020. Ok, so you have to do a little work and tap the ends of the extrusions. Nearly everyone on our team knows how to tap metal now! Oh, and in order to get good 90 degree joints, you really need to have a very good miter saw with a non-ferrous metal blade to cut the 1010 extrusions very cleanly, very accurately. A band saw or hack saw, in my experience, will not do.

We also use a fair amount of polycarbonate. We either use the AM perforated sheets (to mount electrical components) or multi-wall polycarbonate, which is exceptionally strong and light, useful for mounting very light components, or as a modest armor plating, to prevent incidental intrusions of other robots/game pieces to interfere with our robot's internal wiring. We will typically buy a sheet, and have it cut to 2'x4' to ship it cheaply.

Steel pillowblocks, various components from AndyMark, VexPRO, and/or McMaster Carr typically comprise the rest of our robots.

For us, with very modest machining capabilities, simplicity of fabrication is paramount.

[Rohawk1]

Last year, we integrated a mixture of 3d printed Ultem and Titanium into our robot. We also used woven carbon fiber structures for the chassis. Our robot was light, yet extremely strong.

[Wayne Doenges]

FRC Team 1501 T.H.R.U.S.T. uses .062 aluminum sheets and just a few rivets

[DELurker]

Originally Posted by BBray_T1296

I have never seen a team use .125 thick 1" tubing. Everyone I've seen (including our team) uses .0625 (1/16") wall thickness, which, without running numbers (or Google-ing), should end up roughly 1/2 that weight per foot.

*small voice*
In 2012, 1370 built their frame out of 2"x1" aluminum box with 1/8" walls. We then bought a 1-3/8 hole saw and had students use our Bridgeport vertical mill to lighten the aluminum parts at very precise repeated intervals. The end result was a robot which was 119.9 pounds without a shooter.

Of course, that also meant we could balance with anybody on the bridges and we could move any fender-shooters off their mark without any real effort....

In 2012, we used 1" square 1/16" wall aluminum box tubing and worked up a pretty decent offensive robot.

Moral: Never using 1/8" wall aluminum tube again.

[FS Robotics]

I am on a FIRST Rookie team and have a question about supplies. Are there any parts and tools that my team will definitely need during build season that does not come with the Kit of Parts? We would like to purchase these before build season if it is possible, but have no idea what items to buy.

Thank you for your help!

[Mark McLeod]

The KOP only gives you a basic drivable base, so there is a lot more you'll need to beg, borrow or buy.

You'll need raw material for any superstructure/manipulators/mechanisms, additional speed controllers to control any motors beyond the basic drive motors that you'll get.
You may need to purchase extra 12v competition batteries, more (FRC legal) motors, nuts & bolts, rivets, tools, the list goes on for quite a while.

If you have a nearby veteran team then visit them to look at last year's robot. or find photos online of robots. Most of what you see will need to be added over and above what the Kit supplies.

You may not know what all you may need until the game is revealed and you settle on a robot design.